Hydrogen peroxide decomposition control with alkaline earth metal carbonates



April 8, 1969 RESIDUAL PEQOXIDE TOTAL).

W. E. HELMICK ET AL HYDROGEN PEROXIDE DECOMPOSITION CONTROL WIT ALKALINEEARTH METAL CARBONATES Filed Oct. 28. 1966 90 O H O; NaOH Nm Si0 PH[0.58

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United States Patent HYDROGEN PEROXIDE DECOMPOSITION CONTROL WITHALKALINE EARTH METAL CARBONATES William E. Helmick, Doylestown, andBlaine 0. Pray, Wadsworth, Ohio, assignors to PPG Industries, Inc.,Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 28, 1966, Ser.No. 590,324 Int. Cl. C091; 3/00 US. Cl. 252-186 6 Claims ABSTRACT OF THEDISCLOSURE Alkaline earth metal carbonates in amounts of 0.00 to 1percent by weight are added to aqueous alkaline hydrogen peroxidecontaining bleaching baths to control the rate of hydrogen peroxidedecomposition.

The present invention relates to hydrogen peroxide bleaching. Moreparticularly, the invention relates to improvements in hydrogen peroxidebleaching solutions. Still more particularly the present inventionrelates to the controlled decomposition of aqueous, alkaline hydrogenperoxide bleaching baths.

Sodium silicate has been used to control the rate of decomposition ofhydrogen peroxide in hydrogen peroxide bleaching solutions for manyyears. While sodium silicate represents a suitable material for thispurpose, it causes difficulties during the continuous bleaching ofcotton goods and/or cotton and synthetic blends. Sodium silicate tendsto deposit on the surface of stainless steel processing equipmentutilized in continuous bleaching ranges and these deposits build upafter continuous use, thus forming a rough scaly surface on thisprocessing equipment. When fabric passes over the scale deposits,abrasion of the fabric occurs resulting in increased processing costsdue to loss of fabric. The removal of silicate deposits on steelprocessing equipment becomes quite diflicult and they are typicallyremoved by recourse to grinding the stainless steel surfaces. This, inturn, requires the disassembly of parts from a continuous bleachingrange and a consequent interruption of production causing additionalcost. A further difficulty involved in the utilization of sodiumsilicate for the control of decomposition rates of hydrogen peroxide inbleaching baths involves the depositing on the surface of the fabricbeing processed during the bleaching operation of sodium silicate. Ifdeposition does occur on fabric prior to dyeing of the material, crowsfeet or uneven dyeing results on the cloth. This deleterious effectrepresents an additional cost due to reprocessing of the fabricnecessitated to obtain level dyeings. In some cases, the fabric is notcapable of being reprocessed and is consequently ruined.

In accordance with the present invention, many of the diflicultiesencountered in the prior art utilization of sodium silicate forcontrolling the rate of decomposition of hydrogen peroxide and hydrogenperoxide bleaching solutions are overcome. Thus, the utilization of analkaline earth metal carbonate as in alkaline hydrogen peroxide bleachsolutions provides a material which does not easily form on the surfaceof either fabric or processing equipment in solid form. It has beenfound in accordance with the instant invention that the utilization ofalkaline earth metal carbonates, notably barium carbonate, calciumcarbonate and strontium carbonate, not only provides a controlled rateof decomposition of hydrogen peroxide utilized in hydrogen peroxidebleaching solutions, but also results in a bleaching solution which isnot detrimental to processing equipment utilized in continuous steelprocessing equipment. Still further, any tendency for any carbonateformation on the surface of steel equipment or the fabric itself can beeasily eliminated by pH control of the bleaching solution. Thus, the artis provided in accordance with the instant invention with a suitablesubstitute for sodium silicate in the control of decomposition ofhydrogen peroxide in hydrogen peroxide bleaching solutions.

In treating bleaching baths in accordance with the teachings of theinstant invention, a quantity of alkaline earth metal carbonate of from0.005 to 1 percent by weight is typically employed. Preferably alkalineearth metal carbonate concentration is from 0.3 to 0.8 percent byweight.

In order to achieve the full benefits of the effect of the carbonates ofthe instant invention, it is desirable to maintain a pH in the bleachingbaths of from 7 .5 to 13, preferably from 9 to 12. Maintaining pH inthis range can be readily accomplished by adding quantities of alkalimetal hydroxides or other soluble base to the bleaching baths as needed.It will be obvious that in some instances the use of alkali metalhydroxide for pH control may not be required. So long as the solution ofH 0, containing alkaline earth metal carbonate has a pH in theaforementioned range, there is no need for additional alkali additionthereto.

In general, the alkaline earth metal carbonates of the instant inventionimpart to aqueous hydrogen peroxide bleaching baths a controlleddecomposition of the hy drogen peroxide. Typically hydrogen peroxidebleaching solutions contain on a weight basis 0.1 to about 2 per cent H0 by weight. Preferably, these solutions are maintained with an H 0content of between 0.1 and 1 percent by weight. With hydrogen peroxidebleaching solutions of this concentration having a pH from 7.5 to 13 andnot containing any sodium silicate, it is now possible with the instantinvention to provide a controlled rate of decomposition of peroxideformerly achieved with sodium silicate using alkaline earth metalcarbonate. The precise mechanism by which this decomposition occurs orwhy decomposition of H 0 in such bleaching solutions is controllablypermitted with alkaline earth metal carbonate is not fully understood.The presence of the carbonate ions in solution may be a determiningfactor or it may be the presence of both the carbonate and alkalineearth metal ions in association with the peroxide that imparts thebenefits. Whatever the mechanism it has been discovered that a hydrogenperoxide bleaching bath without sodium silicate can be made tocontrollably release oxygen from hydrogen peroxide by providing analkaline earth metal carbonate thereto and in concentrations of between0.005 and 1 percent by weight at an aqueous hydrogen peroxide pH ofbetween 7.5 and 13. Since no deposition of scale on process equipmentoccurs, the substitution provides benefits in the over-all processingcosts involved in utilizing these bleaching solutions on continuousbleaching ranges where cotton and synthetic blend fabrics are employed.

.4 manner by immersion in a 3 percent by weight sodium hydroxidecontaining 0.1 percent by weight Sandopan D.T.C. The cloth was padded toa 100 percent pickup of solution, steamed for one hour at 212 F., washedwith water and dried.

The dried cloth was then padded to 100 percent pickup of solution withthe various bleach baths listed in Table 1. Each sample after pickup ofthe bleaching solution was steamed for various times as indicated inTable I and at 212 F., washed, dried and subjected to measurement of itsreflectance. The results of these runs are shown in Table I.

TABLE I Securing Steam Bleaching Steam Reflectance 1 Run No. time timepH NaOH SrC 03 (min.) H202 NaOH NazSlOa SrC 03 (min) Blue Green(percent) (percent) (35%) (percent) (percent) (percent) (percent)(percent) 1 Measured on a Hunter multipurpose reflectometer.

tion to time. Also shown is a plot of the same residual peroxide as apercent of the total peroxide in the starting aqueous solution ofperoxide with sodium silicate as the stabilizer.

The following example details the method employed to obtain the plots ofFIGURE 1.

EXAMPLE I All decomposition studies were made by utilizing a five neckreaction flask of one liter capacity mounted in a constant temperatureoil bath. The flask was equipped with stirrers passed in through one ofthe necks. A thermometer was inserted into the flask through anotherneck and two of the remaining three necks were filled with ground glassstoppers to serve as sample parts. The remaining neck was fitted with aset of condensers in tandem, both condensers being water cooled.

All solutions were prepared by adding all ingredients except thehydrogen peroxide to deionized water. When the solution of theingredients for each run was effected the solution was placed in theflask and the temperature of the solution elevated by the oil bath to 95C. When the temperature was lined out at 95 C. the hydrogen peroxide wasadded by pipette volumetrically. When the addition was complete, 1minute was allowed for thorough mixing. A 10 milliliter sample was takenby volumetric pipette and called the zero sample time. Additionalsamples were then taken at 3, 6, 9, 12, 15, 30, 45 and 60 minutes. Theperoxide content of the samples was then determined by volumetric methodusing a permanganate titrated similar to the test outlined on pages 553and 554 of Schumb et al., Hydrogen Peroxide, 1955, Reinhold PublishingCorp., N.Y.

EXAMPLE II In all experiments 80 by 80 count cotton print cloth was usedto test bleaching effectiveness. The fabric was scoured in causticbefore bleaching in the conventional As will be readily appreciated fromthe above table, the use of alkaline earth metal carbonate, notablystrontium carbonate, produces adequate bleaching of cloth and comparesfavorably with sodium silicate containing peroxide bleaching baths.

While the above examples show the utilization of strontium carbonate,barium and calcium carbonates can also be employed. When used bothbarium and calcium have been found to be effective in producing acontrol on the decomposition of hydrogen peroxide bleach baths whilepermitting such baths to perform effectively in the bleaching of cloth,particularly cotton cloth and blends of cotton and synthetics such aspolyurethane, nylon, orlon and the like.

In utilizing the alkaline earth metal carbonates it is an importantconsideration that substantially pure chemicals (99.99 percent purity)be employed. Thus, reagent grade material is preferred and was employedin all the above examples.

Further, while the invention has been described with particularreference to the use of hydrogen peroxide bleaching baths, it is ofcourse to be understood that it can also be employed in peroxide bleachbaths prepared from inorganic and organic peroxides such as sodiumperoxide, benzoyl peroxide and complex peroxy hydrates such as aredescribed in US. Patent 3,140,149.

While the invention has been described with reference to certainspecific examples, it is not intended to be so limited except insofar asappears in the accompanying claims.

What is claimed is:

1. An aqueous alkaline hydrogen peroxide containing bleaching solutioncontaining a concentration of from 0.005 to 1 percent by weight of analkaline earth metal carbonate sufiicient to control the rate ofdecomposition of the hydrogen peroxide wherein the pH is from 7.5 to 13.

5 2. The bleaching bath of claim 1 wherein the alkaline earth metalcarbonate is strontium carbonate.

3. The bleaching bath of claim 1 wherein the alkaline earth metalcarbonate is calcium carbonate.

4. The bleaching 'bath of claim 1 wherein the alkaline 5 6 ReferencesCited UNITED STATES PATENTS 5/1916 Schaidhauf 252-186 1/1958 Feldmann252-186 X LEON D. ROSDOL, Primary Examiner. I. GLUCK, AssistantExaminer.

US. Cl. X.R.

U.S. DEPARTMENT OF COMMERCE PATENT OFFICE Washington, 0.6. 20231 UNITEDSTATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 ,437 ,599April 8 196' William E. Helmick et a1.

It is certified that error appears in the above identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 5, line 9, "earth carbonate" should read earth metal carbonateSigned and sealed this 7th day of April 1970.

(SEAL) Attest:

WILLIAM E. SCHUYLER, J

Edward M. Fletcher, Jr.

Commissioner of Patent Attesting Officer

